Imaging flow cytometry couples a microscope with a microfluidic channel in order to image a sample, such as individual cells. The most advanced commercial imaging flow cytometer is presently the Amnis® system, which captures widefield images of the sample while the sample flows in a microfluidic channel. Widefield imaging, however, often has reduced contrast due to contamination from the out-of-focus background. Other microscopy techniques, like confocal and multiphoton, can produce images with higher contrast but are difficult to adapt to use in flow cytometry due to their slower frame rates and use of point scanning. The use of a light sheet microscope instead of widefield imaging results in an image with higher contrast but also permits the use of a higher frame rate than even a confocal microscope. The use of a light sheet microscope also permits for the construction of a three-dimensional (3-D) image of the individual cells with lower phototoxicity than a confocal microscope.
Light sheet microscopy functions by generating a thin (generally on the order of 1 μm) sheet of light that passes through the flowing fluid. This thin sheet captures a single plane of the sample as it passes through the sheet. Because the frame rate on the light sheet microscope is very high, rapid capture of successive planes of the sample is possible, permitting the construction of the three-dimensional image.